1. Field of the Invention
The present invention relates generally to keypad assembly used in electronic devices such as mobile phones, hand held device, or the like, and more particularly to keypad assembly for selectively operating in a mechanical metal dome mode or a capacitive touchpad mode.
2. Description of Related Art
Portable electronic devices, such as mobile phones, hand held device, or the like, include a keypad assembly having one or more keys as a data input unit. A user conveniently inputs alphanumeric or symbol characters and selects a desired function using the keypad assembly.
A conventional structure for a mechanical metal dome mode of the keypad assembly is constructed as follows: one or more metal domes are attached at predetermined contact points on a printed circuit board, a silicon keypad rubber with a predetermined thickness, on which corresponding responding protrusions are formed, is stacked on the printed circuit board, and a keypad buttons are attached on the silicon keypad rubber. In recent years, a structure for a touchpad mode is constructed as follows: films having corresponding electrodes cross each other on the printed circuit board to form a coordinate system, and a dielectric layer is interposed between the films. Accordingly, when a user touches the keypad assembly, capacitance at the touched position is changed, such that corresponding data are input by detecting the capacitance change.
Recently, a new keypad assembly for allowing the selection of the mechanical metal dome mode or the touch mode is instructed. It is configured by stacking the structure for the touch mode on the structure for the mechanical metal dome mode. Obviously, the whole thickness of such a stacked structure is increased and same to the whole volume of the electronic device.
Therefore, a keypad assembly having a reduced volume is desired.